to fuck someone on a moving train and go all the way, meaning for both partners to achieve orgasms and cum (or "come"). starts with groping people on crowded trains where most of the people are working men. derived from the hentai anime "g spot express"
Dave: Dude, I just boxed that girl on the train on the orange line.
Steve: I can tell from the odor coming from your unzipped fly and red face.